The present invention relates to a display driver and a display panel module, and a technique applicable to any of COG (Chip On Glass) mounting and COF (Chip On Film) mounting, e.g., a technique useful in application to a display driver operable to perform the display driving of a liquid crystal display panel.
In a display panel such as a liquid crystal display panel, display elements and signal lines for supplying drive signals to the display elements are formed on a glass substrate. The pitch of signal lines can be formed on a glass substrate with high precision and it can be made narrower than the pitch of wiring lines formed on a film such as a flexible printed wiring board (FPC).
Examples of the form of mounting a display driver used for display driving of a display panel, such as liquid crystal display panel, include COG mounting and COF mounting.
The COG mounting is a form of directly mounting a display driver of a bare chip (or a semiconductor chip shape) on a glass substrate on which display elements and transparent electrodes are formed. The mounting form is suitable for a high-speed action because of a smaller wiring load to a display driver. For instance, a semiconductor chip for display driving, which is suitable for COG mounting is shown by example in Japanese Unexamined Patent Publication No. JP-A-2008-145477. In the semiconductor chip, two rows of external output terminals for drive signals are arrayed along a lengthwise direction of the chip, and the two rows are displaced from each other in the lengthwise direction by about one half pitch. Further, the external output terminals of the rear row are led out through between the external output terminals of the front row and then, connected to signal lines of a display panel concerned. As described above, the pitch of an array of output terminals of a display driver to be mounted by COG mounting, i.e. the wiring line pitch of a wiring pattern on a glass substrate, to which the output terminals of the driver are connected, tends to get narrowed.
The COF mounting is a form of mounting a display driver of a semiconductor chip shape to a wiring pattern on a wiring circuit board in, e.g., a polyimide film. The wiring line pitch of a wiring pattern formed on the film inevitably becomes larger than the wiring line pitch of a wiring pattern formed on a glass substrate. A semiconductor chip of display driving use, which is mounted by COF mounting is shown by example in JP-A-2006-13421.
Hence, it is often the case that COG mounting is applied to a display driver of a display panel of high resolution such as FHD (Full High Definition), whereas COF mounting is applied to a display driver of a display panel of low resolution such as VGA (Video Graphics Array), of which the wiring pattern pitch of the display panel electrode is made relatively wide.